Ignition system



Feb. 14, 1950 G. 1.. LANG 2,497,307

IGNITION SYSTEM Filed June 6, 1946 3 Shets-Sheet 1 BEEA-K 51a GEEGOR L. LANG.

I u E INVENTOR. IQ

ATTO ENE Y Feb. 14, 1950 G. L. LANG IGNITION SYSTEM 3 Sheets-Sheet 2 Filed June 6, 1946 2 G j w w s s R n d 2L||L.| G s e BOOST ENETQGY SELECTOR SWITCH INVENTOR. 6125.602 L. LANG.

ATTO ENE: 3

Feb. 14,1950 G. L. LANG' I 2,497,307

IGNITION SYSTEM 5 Sheets-Sheet 3 Filed June 6, 1946 INVENTOR.

GEEGOE L. LANG.

ATTOPNE Y iate'nted eh. 14,

IGNITION SYSTEM Gregor L. Lang, Longmeadow,

American Bosch Corporation,

Mass., assignor to Springfield,

Mass, a corporation of New York Application June 6, 1946, Serial No. 674,724

8 Claims.

This invention relates to ignition systems such as are used on internal combustion engines and has particular reference to the provisions of improvements in high frequency ignition systems of the type shown generally in U. S. Patent to Whisler 1,376,846, granted May 3, 1921, and wherein, as illustrated diagrammatically in Fig. 1, a magneto or battery and induction coil is employed as a source of energy which charges condenser C until it reaches a voltage sufficient to jump across gap G The energy previously stored in condenser C discharges through said gap G and the primary P of a high ratio, radio frequency Tesla type transformer. This discharge is of a high current, steep wavefront variety and of a damped oscillatory nature and such discharge in the primary of the Tesla coil gives rise to high voltage oscillations of similar waveform but magnified amplitude in the secondary S and the secondary discharge is used for ignition purposes in the spark plug G Such systems have been found to possess certain advantages over more conventional high tension, low frequency battery coil or magneto systems in that they were capable of reducing spark plug erosion, improved ability to fire consistently in spite of oil, carbon, and lead fouling of the spark plugs, and reduced tendency to fiashover externally at high altitudes when employed in 7 modern reciprocating type aircraft engines, however, such systems contain certain inherent limitations. For example, the secondary discharge of the Tesla type coil is of a low current, low energy type and low in heat value as compared with more conventional hightension systems, and the high frequency spark is of a very limited ignition value when extremely cold weather starting conditions are encountered or. when the fuel employed is of a cruder and less volatile type than gasoline, which drawback has heretofore practically eliminated the high frequency ignition system as a method of igniting jet propulsion motors, oil burners, fuel oil and kerosene engines and the like.

From the foregoing it will be seen that the inherent anti-fouling characteristics of the high frequency or capacity discharge type of ignition system would be most advantageous in those applications if the inherent disadvantages of such systems could be overcome, particularly if a hotter and higher energy spark discharge could be obtained which was not possible with prior constructions wherein the energy per pulse or discharge is definitely fixed by the fundamental energy equation for a charged condenser,

Where E is the energy in joules, C is the capacitance in farads and V is the voltage to which the condenser is charged.

It is, therefore, the principal object of this invention toproduce anignition system or circuit which combines the high energy, high current and high heat value ofv a low frequency system with the anti-fouling and other advantages of a high frequency system.

Another object of the invention is to provide an ignition system or circuit of the type set forth in which the electrical energy per discharge may be preadjusted to desired value.

Another object of the invention is to provide an ignition system or circuit in which the electrical energy per discharge may be manually or automatically varied during operation whereby high spark energy may be utilized for starting or operation with low grade fuels and in which the spark energy may be reduced to minimize spark plug erosion during running periods of the engine,

Another object of the invention is to provide a new and improved ignition system or circuit which provides the anti-fouling qualities of a high fre-. quency system and the high energy, hot spark qualities of the conventional high tension system,

Another object of the invention is to provide a new and improved ignition system which produces a relatively high energy ignition spark and in which the energy value is not substantially affected by ignition gap length, compression pressure or other variables.

Another object of the invention is to provide an energy booster circuit as an addition to a high frequency circuit.

Other objects and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawings and it will be understood that many changes may be made in the details of construction and arrangement of parts shown and described, as the preferred forms have been shown by Way of illustration only.

Referring to the drawings:

Fig. 1 is a diagrammatic view of a prior art form of high frequency ignition system;

Fig. 2 is a diagrammaticview of the basic circuit of the present invention;

Fig. 3 is a fragmentary view showing part of the circuit shown in Fig. 2 and showing the effect of serious fouling across the gap of the spark plug;

Fig. 4 is a view similar to Fig. 3 and showing means for overcoming such fouling;

, Fig. 5 is a fragmentary view showing a modified'form of the invention;

Fig. 6 is generally similar to Fig. 5 but shows a slightly different form of the invention;

' Fig. 7 is generally similar to Fig. 2 but shows a portion of the circuit common to all of the spark plugs or engine cylinders instead of a separate circuit for each plug or cylinder;

Figs. 8 and 9 are fragmentary views of the form of the invention shown in Fig. 7 but showing modified arrangements.

Referring more particularly to the drawings whereinvsirnilar reference characters designate corresponding parts throughout, the form of the invention shown in Fig. 2, includes, in addition to the elements contained in the prior construction shown in Fig. 1, some of which has been pree viously described, the condenser G2 which is connected in series between the normally grounded end of the Tesla coil secondaryLzand'ground G; and the resistor RI which provides a path through which the condenseryCl: receives, its

charge from the common power source simultaneously with condenser C.

As will be seen from Fig. 1, in prior type conventional oscillatory-ignition circuits orsystems, the only energy delivered "to the ignitionspark gaps or spark plug is a portion of'the: energy originally stored intcondenser Cl, translated-in frequencyby the primary zcircuit; transformed in voltage by the Tesla coil andrconductedxtozthe firing; electrodes. In "such a, circuit .or, system a considerable portion of the,-original stored energy is: lost in this process, due;.to-.various. losses inherent to the circuit. Aniapproximationxof the energy actually reachingthe ignition-gap may be made by applying:the I basic energy equation .pre-, viouslystated,

V T to both the primaryand secondary, circuits.

Ifwe assume, for example, thatthe primary storage condenser C| has a capacitance of .006 microfarad (mid) chargedto,apeakvoltage of 2 'kv. giving an energyvalue of .012 joule or'12 millijoules, and that in thersecondary, circuitthe crest "voltage may reach a value ofv 16, kilovolts across a total capacitance of'25 'micromicrofarads, which. equals .0032 joule or 3.2 Q millijoules (mil), the indicated conversion .efliciency based on the ratio of 3.2 to 12,. is 26.7 per cent; In the case of a primary break-down value of '22 kilovolts, the energy'stored wouldbe approximately millijoules, giving a translation eifi'ciency of 21.5per cent.

It is apparent that anyattempt-to materially raise the spark energy at the ignition spark: gap by-increasing the stored energy in the primary circuit would place uporrthe magnetoor battery coil a burden likelyto be beyond'its capabilities, for example, to double y thesecondary spark energy from 3.2 mi. to 6;4'mj. would-require-a primary circuit energy of from 25to 30*mj. and most conventional ignition coils would not be expected to operate under *sucha-conditiom and further, even if such secondaryspark energy wereraised from'3.2 mj.'to 6.4 mi, it would not.

be suificient for starting-purposes when extreme conditions of coldweather, oilfouling or frost fouling of spark plugs were encountered, and it is possible that even'l5 tomi. of energy would be required at the ignitiongap under such conditions. This is entirely outof the-question with prior systems of this type.-

The system or circuit of the present invention is capable of making an energy of 15 to2O -mj.

available at the igniting gapyfor startingpurposes, without exceeding the energy potentiality of standard conventional ignition-coils,

andinladdition: can be constr'ucted to provide switching means for reducing-the energy :at the. igniting gap, after the engine. starting has been: successfully accomplished, for the purpose of .4. minimizing spark plug electrode erosion. This switching or controlling means may be arranged to completely eliminate the energy boost employedjfor'qstarting purposes and cause the system to revert to a straight or normal high frequency system operating at a predetermined ignition gap energy of from 2 to 5 mj., or it may be arranged to permit operational adjustment of ignition gap energy at any desirable intermediate level between the .20 mi. maximum boost level and the zero boost or straight high frequency system level of from 2 to 5 mi.

In the circuitsor systems of both Fig. 1 and Fig. 2,-there is shown for the purpose of explaining the invention only a-system for a single spark plug, and it is of course obvious that to adapt the circuit or system to any 'desirednumber of spark plugs, or'enginejcylinders that it would only be necessaryto' provide each spark plug or engine cylinderiwith all of'the high frequency conversion components except the .energy source and distributor;

As previously stated,"tlie system of the present invention, as shown in.Fig.z2; has in addition to the elements of the prior type as shown in Fig. 1. a boost or auxiliary storage condenser C2, in a series connectionbe'twee'none end, L2of the Tesla coil'secondaryl S and'ground; andthetresistor Rl', which may, optionallybe aradiolfree quency choke, which serves .to.p rovide a. path through which theboost condenser C2 maybe charged in parallel with the high frequency storage or primary condenser C'I.-

It will be noted. :that' both condensersiCl. and C2 will be charged inparalleland approximately simultaneously by 'the voltage or energy pulse originating. in theasecondary winding of the energ source.-

The impedance RI which :may be. a resistor or a reactance' coili required to effectively isolate the primaryand-v secondarytcircuits in a-radio frequency sense during the discharge which fol lows the completion ofathecharging .of thewtwo condensers and the resulting breakdown .of the primary circuit spark .gap GI.

To better explain; the; invention, the following example is givenvfor whichpurpose-the :following values have been assumed: energy source. 25 mi. per pulse atv 2100 .v. peakpconverter: cone denser CI, .004 mfd-.; boostxcondenser:C2,: .006 mfd.; isolating resistor R I; 12000 ohms; converter gapaGi, breakdownaat 2000nv. peak; ignition gap G2, breakdown:at. 4000 v. peak minimum.

With theswitch Sl closedgas shown'iri Fig. 2, the condensers :CI and'CZ will receive simultaneous charges from the rising voltage due'-to the pulse of energy originatin inthemagneto or-batterycoil secondary: Condenser C] will lag slightly behind condenser C2, due to a slight phase shift introduced byfresistorRl connected in the circuit between'cond'enser Cl and theVOlt-T age source. Foran energizingpulse wavefront having an-800 cycles, per second characteristic, the instantaneous voltage across condenser CI will be approximately 96;per ,cent of'that across condenser C2 .at anyinstantiduring thecharging portion of the, operating. sequence.-v ItLfollows that the voltage across condenser; Cl. appearing across gapGl will reach, the 2000 v..breakdown and high :breakedownwaluav will; have reachedia" denser CI and .012 joule in condenser C2, making a total of .020 joule.

The breakdown of gap GI now follows with the resulting rapid conversion of the stored energy from condenser CI into high frequency oscillatory energy, with the oscillation involving condenser CI, the gap GI and inductanceP; A portion of this oscillatory energy is transferred by inductive coupling from the Tesla coil primary to the secondary circuit, where itappears in a high voltage form across the ignition gap G2.

The discharge across ignition gap G2 is up to this point, a normal high frequency discharge and if no charge resided in condenser C2,{ the hi h frequency discharge across gap G2 would continue in a normal manner to extinction. However, the charge stored in condenser C2 now finds a discharge path open to it, through the closed circuit which includes the transformer secondary S, the ionized ignition gap G2 and return through ground. The resulting surge of current or oscillatory discharge due to condenser C2 and the secondary coil S, occurs at a much lower frequency than that of the condenser CI and primary P circuit, and two beneficial results accrue from this fact. One is an intensification and prolongation of the ionized or are discharge across ignition gap G2, that is, the discharge initiated by the condenser CI and primary P circuit is continued and prolonged by the condenser C2 discharging through the secondary S; the

other is that the primary circuit which includes condenser CI and primary P is anti-resonant at the much lower oscillating frequency of the circuit which includes condenser C2 and secondary S, and thus only a negligible part of the condenser C2 energy is drained off into the condenser CI and primary P circuit by inductive coupling. This permits practically all of the condenser C2 energy to be expended or dissipated in the form of useful heat at the discharge arc" of ignition gap G2.

The second or boost condenser C2 of the present invention provides two principal operational advantages over the conventional high frequency system. One is a material increase in crest current value'with a corresponding increase in arc intensity at ignition gap G2 and the other is the prolongation of the arc discharge at ignition gap G2 for some considerable period of time after the oscillation of the initiating circuit (gap GI' and primary P) has decayed to a substantially zero amplitude.

It will be seen that in the above described circuit or system that the relative amounts of energy given up at ignition gap G2 as useful heat by the two discharge circuits will vary great y.

Assigning a conversion efficiency of 25 per cent to the converter circuit consisting of condenser CI, primary P, and gap GI, an energy value of tion to reduced boost for continued operation or .the form of a bi-metal or other type of thermal the spark plug electrodes during warm running 0 results in a total gap energy dissipation of .0116 joule.

When switch SI is opened, the boost circuit is rendered inoperative and the system reverts to normal high frequency operation, without appreciable assistance or hindrance from the condenser C2, with an ignition gap G2 energy level of .002 Joule.

It is pointed out that the energy stored in condenser C2 is held retained in storage and cannot in itself initiate a discharge at gap G2 until a discharge path is presented to it by the discharge of the CI, P and GI circuit. The two discharges are overlapping and merge into the other without detectable or measurable separation.

It has been found that the operation of the boost circuit does not substantially detract from the excellent anti-fouling characteristics of the high frequency system with which it is associated.

From Fig. 3 it will be seen that the existence of a serious carbon or moisture fouling shunt R2 across ignition gap G2 would tend to discharge condenser C2 or prevent its acquisition of a full charge during the charging period by acting as a resistance shunt in parallel across both condenser C2 and the energy source. This has been found not to be a serious drawback unless the fouling shunt R2 approximates a value of 15,000 ohms or less and in such cases the addition of a series protective gap G3 in series with the Tesla coil secondary S, as shown in Fig. 4, may provide a partial solution.

The switch SI, Fig. 2, may be arranged to providemanual or automatic cut-ofi of the boost circuit after the engine start has been successfully accomplished. This switch SI could be in switch arranged in appropriate thermal relationship to some part of the engine such as the exhaust manifold cylinder head or cooling fluid. The warming up of the engine would then cause the switch SI to be broken and thereby disconnect the boost circuit for such time as the engine may remain at an elevated temperature.

This disconnection of the boost circuit serves to minimize or eliminate unnecessary erosion of periods of engine operation. The straight or normal high frequency system is usually capable of effective continued running of an engine after the cold run-in period is past.

An exception to the above might be an engine running on low grade fuel in which case the thermal switch might be of the doublefacting snap type as indicated in Fig. 5 and in this case the system would operate on high boost for starting and drop by manual or automatic switch operarunning.

In Fig. 6 a modified form of the arrangement of Fig. 5 is shown wherein the boost energy is smoothly and continuously variable through the range of maximum boost to substantially zero boost by manual or automatic manipulation or adjustment of the potentiometer R3.

In Figs. '7, 8 and 9 are shown arrangements whereby a single common boost circuit may be employed for any desired number of cylinders which are to be operated by the same ignition system.

In the form shown in Fig. '7 a tertiary winding as specified would make the use of such a common boost circuit possible. In this case the secondary return leads S2 of the secondaries S of the several Tesla type transformers are made 1 icornmon:and'ireturnedto ground ithrodghzavcommon boost condenser C2. In this case the coma mon xcondenser-.;C2 is .cher ed. and-discharged in a I .t rapid :mannerg'andris. used ssuccessivelysine conjunction with ..the,. various :high v: frequency. converters :as selected :by the: distributor.

Thegsame resultmight be:obt ained;.with.further economy in construction by utilizingiithe v structuresaof Figs: 8 and 9.z

'In': Fig. 8,1 the common: boost..condenser-.;C3lis .1 fedizfrom an intermediateitap rim-the secondary :coiL S of the ienergizingrsourcep In'Fig. 9 the .chargingenergy for the condenser C3= obtained from :it'ne. primary circuit-of :the ignition system....It-.'Wil1ibe noted that rin'Figc 9 azthe condenseriCs. is connected directly incparallel 'withftheprimary. breaker condenser'iC ti and: might -.;.ther.ef.0rexbes dispensed with entirely;

From the .foregoing itr'will bex seen th'at I; have provided simple; efficient xand: eeonomicalvmeans,

iorzobtaining all of the objects and advantages of:.,the. invention. Havingrdescribed .my. invention, I claim:

Lin-a highirequencyignition system cmpriswing .a.-zcapacitance,ahigh :frequencyr-iransformer .:'.and; sp.ark; gap adapted to furnish:-energy :to a .asp ark .%,.p1ug;. an: auxiliary energy booster circuit adapted to supply. additional energy. to theedischargev ofv the highzfrequency.;.circuit; said booster circuit.:comprising a. condenser I and impedance,

-- inga icapacitance; high.ifrequencyrtransformer :.:and; spark gap adapted to: furnishienergyi. to a :spark plug, ran. auxi1iary;- energysboosterucircuit adaptedto supply:additionalaenergy to the discharge of the vhighifrequency'circuitysaid booster circuit; comprising; a. condenser: andeimpedance and a thermal switch1for:connecting-and disconnectingsaid boostericircuit'to said high frequency circuit.

- 4. In .ahightfrequencyignition systern oomprising;arcapacitance,= high. frequency" :trans-former-v and..;spa-rk gap iadapted to furnish-energy: in a spark .plug,-anzauxiliary energy booster adapted ptogincrease the energy-suppliedthe -spark plug, said booster circuit comprising a condenserseriaL ly, connected .withitheseconda'ry of the Sniglrirequency ignition -.system*and: automatically opwerated switch meansior iconnecting -said booster circuit to said high'frequencycircuit whereby said booster circuit. will ;supply...-additional =:energy #to the discharge of the high frequency: circuit,

- 5;; In combination with a a fhighirfrequenc igni- 8 tiorresystem comprising a capaeitanee; high drequency transformer "and spark gap adapted to furnish-energydo a spark plug; an energy booster circuit. including acondenserand an impedance,

5 said booster circuit being ada'ptedto supply additional energy to the discharge--of-che-hig-h f'requency circuit and a series-*sparkegap for-- isolatingthe -hig h frequency and-booster= circuits from the spark-plug during chargingof said condenser 1 o tO DI'GVGHU- thE diVeI SiOn'lZOf'; energy from said I con- -denser-' duning the charging thereof.

62 1111 -conrbination with-a high fr'equenc-y --ig'ni- 'iti'oni system comprising--a'--capacitance, high fre- .quency.-:transformer= and; spark gap adaptedito furnish energy to a spark plug, an energy booster circuiteomprising a condenser and arr-impedance, said-booster circuit beingadapted to supply addiition'al energy-to the discharge of the high-' ire- :quency circuit and means 'forautomaticallyfdisiconnectingethexcondenser of' 'the' booster circuit from the'spark plug' duringithe charging of said condenserctmprevent: the diversion of energy from said. condenser during 1 the charging thereof '7.5,Intcombinationwith ahigh frequency ignisystem comprising -a capacitance; high irer .quency:.-transformer. and.;spark:.-gap adapted to furnish-Energy to .spark. plug,: an energy-booster .-.circuit comprising acondenser and an impedance,

:said ;.booster. circuit being a'dapted to supply: additional energy -.toithedischarge of 'the -high fre- 21 quency; icircuit; and-.means: for automatically dis- .connectingthe .condenser of the -.boostercircuit fromzthe spark plug" during the charging-of said .icondenser. andfor automatically connecting said v condenserto said spark .plugwhen-said condenser .60'- 'denser-gduring .:the :charging. thereof.

TGREGOR LZILANGH REFERENCES ":CIT'ED UNITED STATES PATENTS ---'Number-- i Name I Date- -1,3-'Zfi',846 I Whisler- May 331921 two-1,459,252 PIummi -June'19,'-1923 111;!2453830 Bethenod Feb; 4; I930 1;95.5;520 Vawtep Apia-17,1934 '.:-2,009,125: asmithson July 23; 1935 2;09.0',=36.5f f-Har-ris Aug; '17, 1937 522011784 :I-Iolthouse i Junellf1940 ;.2,:409,202 Francis i Oct.--- 15, 1946 Disclaimer 2,497,3O7.Grego1- L. Lang, Longmeadow, Mass. IGNITION SYSTEM. Patent dated Feb. 14, 1950. Disclaimer filed July 18, 1951, by the inventor, the assignee, American Bosch Gomomtz'on, consenting. claimer to claim 1 of said patent.

Hereby enters this dis [Oyficial Gwzette August 11;, 1951.] 

